The invention relates to a hybrid high-voltage substation having busbars and disconnectors that are enclosed in metal cladding and insulated with gas using metal-clad and gas-insulated technology, and its other equipment that is insulated with air using conventional air-insulated technology. More particularly, the invention relates to an improvement to that type of substation, consisting in adding a backup phase using conventional air-insulated technology, so as to make it possible to reduce significantly the time for which the substation is unavailable while work is being done on the busbars. It should be noted that the abbreviation GIS (for xe2x80x9cGas-Insulated Systemxe2x80x9d) is commonly used to designate metal-clad and gas-insulated technology applied to xe2x80x9cmetal-cladxe2x80x9d switchgear, and that the abbreviation AIS (for xe2x80x9cAir-Insulated Systemxe2x80x9d) designates air-insulated technology.
By way of introduction, the concept of a xe2x80x9chybridxe2x80x9d substation should be explained, because it is relatively recent. The main aim is to reduce the ground area occupied by conventional AIS substations, while retaining both the advantages of AIS technology in terms of cost and of the ease with which components can be replaced, and also the advantages of GIS technology in terms of compactness and of insensitivity to pollution.
It should be recalled that the drawbacks of GIS technology as compared with AIS technology are mainly that costs are higher, and that maintenance and extension are more complex, which means that the substation can be unavailable for as long as a few days. The advantages of GIS technology over AIS technology are mainly that it offers greater compactness, and insensitivity to pollution, in particular at the busbars. In addition, in order to clean the insulators of a GIS substation, it is generally necessary merely to isolate each bay in turn, whereas in order to clean the insulators of the busbars of an AIS substation, it is necessary to isolate all of the busbars.
Forming a hybrid substation consists in progressively replacing GIS-technology equipment with AIS-technology equipment of equivalent function, starting from the equipment situated in the vicinity of an overhead feeder and going towards the busbars. The optimum configuration that satisfies the above-mentioned objectives consists firstly in equipping the substation with metal-clad (GIS) busbars and disconnectors, and secondly in using conventional AIS technology for the remainder of the equipment.
That technical solution procures most of the advantages of metal-clad switchgear and of air-insulated switchgear, without suffering from their respective drawbacks.
In order to optimize ground area occupancy, the Applicant has designed an architecture making it possible to receive the busbars under a central gantry that can serve as a line-stop gantry for feeders on the same side of the gantry. The advantage of such architecture over a conventional assembly using all-AIS technology appears in FIG. 1, in which it can be observed that it is possible to omit the conventional line-stop gantry since it is unnecessary in a hybrid GIS/AIS system. A configuration that has directly mutually opposite feeders, and that is particularly advantageous in terms of ground area used, has also been designed by the Applicant, and is shown in FIG. 4.
However, such hybrid GIS/AIS systems do suffer from drawbacks as compared with systems using conventional all-AIS technology. In particular, when performing maintenance on a metal-clad double busbar set, it is often necessary to de-energize two busbars assigned to the same phase, thereby making the substation unavailable for three to four days on average, because of the complexity of the work on GIS-technology equipment. Firstly, for some types of work, it is essential to de-energize two busbars having the same phase, in particular when doing maintenance on a selector switch disconnector for said two bars. During the work, it is necessary to empty the gas that insulates the compartments of the disconnector and of the feedthrough. Secondly, for other types of work, it is not absolutely essential to de-energize simultaneously the two busbars of the same phase, such other types of work being, for example, extending a busbar set, or adding new metal-clad compartments successively in alignment with existing compartments. The busbars to be extended may be isolated (de-energized) one at a time by the selector switch disconnectors, thereby making it possible to keep the substation in service while the work is being done. However, when performing such work, it is often preferred for both busbars to be completely isolated rather than de-energizing a single busbar only, in order to maximize safety.
Thus, working on metal-clad busbars in a hybrid substation most often involves isolating two busbars of the same phase, thereby making the entire substation unavailable.
An object of the invention is to reduce significantly the time for which a hybrid substation is unavailable when working on metal-clad equipment.
To this end, the invention provides a high-voltage substation comprising firstly equipment implemented using metal-clad technology and constituted by at least one single or double busbar set, and secondly equipment implemented using conventional air-insulated technology so as to form feeders disposed in bays approximately perpendicular to said busbar set, said high-voltage substation incorporating at least one air-insulated backup line approximately parallel to the busbar set and performing the function of backup phase to enable the substation to operate in xe2x80x9cdegradedxe2x80x9d manner.
In a preferred embodiment, each backup line may replace any one of the phases of the busbar set while work is being done a metal-clad element of the substation.
In a preferred embodiment, each backup line is de-energized while no work is being done on any metal-clad element of the substation.
In a preferred embodiment, each backup line is provided with connection elements, each of which is assigned to a respective phase of the feeder that it overlies, and is suitable for being connected to its respective phase via an electrical link element.
In a preferred embodiment, a single backup line is installed on either side of the busbar set. Since an incident in the metal-clad portion of a substation generally concerns a single phase only (each of the three phases is conveyed in a respective independent volume), the backup line may be constituted by a single phase only, thereby considerably reducing cost and considerably increasing compactness.